JP2009060181A - Positional information acquisition system and receiving terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate a position by combining a visible light transmitter and a six-axis sensor in order to to specify a position with high precision indoors. <P>SOLUTION: A positional information acquisition system detects the inclination of a terminal with respect to a gravity vector by a three-axis acceleration sensor 130 mounted on the terminal 100 side, and also detects the direction of the terminal 100 with respect to a geomagnetic vector by a three-axis geomagnetic sensor 140 mounted in the same manner. Information of an absolute position is acquired from positional information transmitted from an LED lighting apparatus (light source) 200, and the absolute position is combined with the inclination and direction of the terminal 100 to estimate with high precision the position where the receiving terminal 100 is present. When the LED lighting apparatus is located within the viewing angle (FOV×2 degrees) of the terminal, positional information from the visible light transmitter is acquired. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to acquisition of position information by visible light communication, and more particularly to a system that can acquire accurate position information.

In recent years, navigation services such as GPS position detection and flat map display have been put to practical use for mobile phones. Examples of the existing main position information acquisition system include the following.
(1) GPS positioning The basic principle of GPS positioning is to measure the distance between a receiver and three satellites, and measure the time required for radio waves transmitted from the satellite to reach the receiver. Thus, the distance to the GPS satellite is converted.
In order to perform GPS positioning, it is required to capture at least four GPS satellites at the same time, and there is a shield between the GPS satellites in tunnels, valleys of buildings, shades, underground malls, and buildings. In some environments, this system will not work, especially for indoor positioning.

(2) Positioning using a communication base station In addition to a positioning method using GPS, there is a positioning method called a cell method that specifies a user's position using a communication base station of PHS or a mobile phone.
Since the range covered by one base station is narrow, a service area is constructed by installing a plurality of base stations. Using this feature, the position is determined from the electric field strength of the plurality of base stations received by the PHS terminal. Is estimated. A service that has been put into practical use is to estimate the position by receiving radio waves from a maximum of 10 base stations, and the positioning accuracy is about 100 m even in urban areas with many base stations.
In this system, since positioning is possible within the service area of PHS, positioning is possible even in a subway or a building where many base stations are installed.
Similarly, a service using a base station is also provided for a mobile phone, but a mobile phone base station has a wider range of several hundreds to several kilometers than a PHS, and positioning is performed. There is a problem that accuracy is lowered.

By the way, in the positioning method in pedestrian navigation, hybrid positioning using a communication base station of GPS or PHS / mobile phone is generally used, but it cannot receive GPS satellite radio waves sufficiently. It is said that the error may be 300 m or more because it is impossible to determine the position in a remote indoor or underground mall, and only positioning using a communication base station is performed.
Also, in positioning using a communication base station, since the cell size of a mobile phone is generally several hundred meters to several kilometers, it is unavoidable to cause a large positioning error in an indoor environment where GPS positioning cannot be used. Absent. That is, positioning in a place where radio waves do not reach is a problem in GPS positioning, and positioning using a communication base station has a problem in positioning accuracy.

As means for solving such a problem, local positioning using short-range radio such as wireless LAN, Bluetooth, RFID, and sensor positioning that complements GPS information with other built-in sensors are being studied.
The principle of location information acquisition by short-range wireless communication is the same as that of a cell system using a mobile phone communication base station, such as a wireless LAN access point (AP), Bluetooth communication device, RFID active tag, etc. The wireless transmitter serves as a base station in the mobile phone, and the location of the AP from which the mobile phone has received radio waves is taken as the location of the mobile phone.
In local positioning, even with the same cell method, the cell radius is smaller than that of a mobile phone base station, so highly accurate position information can be obtained, and radio waves from multiple access points can be used for the principle of three-point surveying. It is expected that more accurate position information can be acquired by performing position calculation.

However, local positioning can be used only in places with short-range wireless equipment, and there are issues such as the need to install an access point, and a sensor that calculates the current position using an acceleration sensor or geomagnetic sensor Also in positioning, there is a problem that accumulation of errors is a concern when using for a long time in a place where GPS radio waves do not reach.
Furthermore, a technology that incorporates a heading-up function that rotates and displays a planar map according to the traveling direction by incorporating a magnetic compass has been put into practical use.

However, since the user is required to associate with the layout of the surrounding buildings in the head only with the flat map display, the surrounding situation can be intuitively grasped in order to realize a more familiar navigation service. Technology has been developed.
It combines GPS and attitude detection technology to detect your position information and the three-dimensional attitude of the terminal you hold in your hand. This is a navigation technique for displaying a target direction three-dimensionally.

The three-dimensional attitude detection technology detects the tilt of the terminal using a three-axis acceleration sensor and detects the direction in which the terminal faces by using a three-axis geomagnetic sensor. Such a six-axis sensor By using (3-axis acceleration sensor + 3-axis geomagnetic sensor), it becomes possible to detect all posture states of the terminal.
These use an acceleration sensor utilizing MEMS technology and a small geomagnetic sensor. By mounting the sensor on a single board together with a CPU for posture detection calculation, the posture detection unit was successfully downsized. In the future, it is expected to be mounted on a mobile phone (see Non-Patent Document 1).
However, in the current technology, only a method using an IC tag such as RFID has been proposed for indoor position detection, and there is a need for infrastructure maintenance.
“Development of composite sensors aimed at mobile phones, automobiles and robots continues. Acceleration, angular velocity, and direction detection in one package”, Nikkei Microdevices, July 2006, p89-91 Toshihiko Kobuchi, Yuichi Tanaka, Shinichiro Haruyama, Masao Nakagawa, “Proposal of Illumination Optical Communication Using White LED” IEICE Technical Report, OCS2001-71, 2001

  An object of the present invention is to perform position estimation by combining a visible light transmitter and a six-axis sensor in order to enable highly accurate position specification indoors.

In order to achieve the object of the present invention, the present invention receives a position information from a light source, a three-axis acceleration sensor, a three-axis geomagnetic sensor, and a light source that transmits information on the installed position by visible light. A visible light receiving terminal including a visible light receiving unit and a calculation unit, wherein the receiving terminal receives the position information of the light source received by the visible light receiving unit, and a three-dimensional posture by the three-axis acceleration sensor The position information acquisition system is characterized in that the position information of the terminal corrected by the calculation unit is calculated based on the information and a three-dimensional orientation by the three-axis geomagnetic sensor.
A visible light receiving terminal comprising a three-axis acceleration sensor, a three-axis geomagnetic sensor, a visible light receiving unit that receives position information from a light source, and an arithmetic unit is also the present invention, and the visible light receiving unit The position information of the terminal corrected by the calculation unit is calculated based on the received position information of the light source, the three-dimensional attitude information by the three-axis acceleration sensor, and the three-dimensional direction by the three-axis geomagnetic sensor. And
The visible light receiving unit can calculate an accurate position by having a predetermined viewing angle.

In the present invention, in addition to position information from a light source transmitted by visible light communication, position estimation is performed by using inclination data of a three-axis acceleration sensor mounted on a six-axis sensor and direction information by a three-axis geomagnetic sensor. The range is limited and the position is estimated with high accuracy.
Thereby, it is possible to estimate the position indoors simply by holding the receiving terminal over the LED lighting apparatus. In recent years, since infrared communication function (IrDA) is installed in almost all mobile phones, assuming the photodiode (PD) of the mobile phone as the receiving terminal, both transmission and reception can solve the problem from the viewpoint of infrastructure development. it can.

Embodiments of the present invention will be described with reference to the drawings.
The outline of this system will be described with reference to FIG.
In this system, by receiving the position information from the visible light transmission device transmitted from the LED lighting apparatus (light source) 200 by the terminal 100, absolute position information like GPS can be acquired by the terminal. Refer to Non-Patent Document 2 for the visible light transmitter and the like.
However, as shown by the large circle in FIG. 1, information from the same visible light transmitter can be received at any location within the irradiation range of the LED 200. An error will occur in the possible area.
In order to avoid this problem and reduce the error within the irradiation range from the visible light transmitter, it is conceivable to limit the field of view (FOV) of the terminal 100. However, when the field of view of the terminal is simply limited, the receivable area is limited to a few meters, so that it is limited to use in a place with a short-range wireless facility, like local positioning such as RFID.
That is, in the position information acquisition system using visible light, the LED illumination 200 is considered as a transmitter, so that accurate position information can be obtained only when the LED is radiated over a wide area and the receiver is directly below. It will be possible.
In addition, since the inclination of the terminal 100 is not taken into account, it can be said that the information is not practical because the information from the visible light transmitter must be received with the receiving terminal facing upward.
Therefore, in this system, considering the combination of 6-axis sensors installed in the terminal 100, by using the tilt data of this 6-axis sensor, it is possible to receive position information from a visible light transmitter other than directly under the LED illumination. Thus, the position is estimated with high accuracy in every place where the position information from the LED illumination can be received.

FIG. 2 is a conceptual diagram of this system.
In the system shown in FIG. 2, the inclination of the terminal with respect to the gravity vector is detected by the triaxial acceleration sensor 130 mounted on the terminal 100 side, and the orientation of the terminal 100 with respect to the geomagnetic vector is similarly detected by the three-axis geomagnetic sensor 140 mounted. Is detected.
Information on the absolute position can be acquired from the position information transmitted from the LED lighting apparatus (light source) 200, and the receiving terminal 100 exists by combining this absolute position with the inclination and orientation of the terminal 100. The position is estimated with high accuracy. When the LED lighting device enters the viewing angle (FOV × 2 degrees) of the terminal (when the LED lighting device is within the field of view of the receiving terminal 100), information from the visible light transmitter can be acquired.

FIG. 3 is a block diagram showing the configuration of the terminal 100.
In the terminal 100 of this system, the position information obtained from the visible light source 200 is obtained by the light receiving element 110 such as a photodiode and the receiving device 120. Further, the tilt and direction of the terminal 100 are detected by a six-axis sensor that combines the three-axis acceleration sensor 130 and the three-axis geomagnetic sensor 140. These pieces of information are calculated by the arithmetic device 150, and an accurate position of the terminal 100 is estimated in consideration of a predetermined viewing angle of the terminal. The position information is displayed on the display 180 by sending the result thus obtained to the display control device 170.
If necessary, the data transmitter 160 can transmit the obtained location information of the terminal 100 to another device.
Thus, in this system, by limiting the FOV of the terminal (receiver) 100, it is possible to limit the communicable area and reduce the positioning error.

In the position estimation in this system, since the position is estimated based on the inclination of the terminal 100, the accuracy is greatly influenced by the height of the LED lighting apparatus (light source) 200 and the receiving terminal 100. Therefore, by adding information on the height of the ceiling to the information from the visible light transmitting apparatus in addition to the position information that refers to the absolute position, more accurate position estimation is expected.
In this case, the arithmetic device 150 estimates the position by using the received position information of the light source 200 and the height information of the light source 200 and the tilt and direction information of the terminal 100.
Thus, by using the 6-axis sensor, positioning can be estimated even when position information is received at a place other than directly under the illumination. In other words, it is a system that enables more accurate positioning simply by holding the terminal over LED lighting.
Since the estimated area has a difference in the communication area according to the inclination of the receiving terminal, position information can be obtained by combining the receiving terminal inclination data and the visible light transmitter.

FIG. 4 is a diagram for explaining that the position is estimated based on the inclination and orientation of the receiving terminal. 4A shows the relationship between the light source (transmitter) 200 and the receiving terminal 100, FIG. 4B shows the rotation angle α of the receiving terminal 100, and FIG. The inclination angle θ is shown.
As shown in FIG. 4 (a), the point B as the LED light source 200 which transmits the position information of the visible light and the coordinates _{(x t, y t, z} t). Further, the center coordinate of the receiving terminal 100 is a point R, and this coordinate is (x _r , y _r , z _r ). The receiving terminal 100 has an inclination in the θ direction and the α direction, and the distance between the transceiver BR is d. The distance AR from the terminal 100 to the ceiling is d _v , and the intersection of the normal line extending from the receiving terminal 100 toward the ceiling and the ceiling is a point C. At this time, ∠ARC is θ, and ∠BRC is ξ. Line segments AR, BR, and AC are
AR = d _v = z _t −z _r (1)
BR = d = √ {(x _t −x _r ) ² + (y _t −y _r ) ² + (z _t −z _r ) ² } (2)
AC = d _v tan θ (3)
The line segment CR extended from the receiving terminal to the ceiling is expressed by the following equation using the line segments AC and AR.
CR = √ (AC ² + AR ² ) (4)
The line segment BC is calculated from coordinates.
BC = √ {(x _r + AC cos α−x _t ) ² + (y _r + AC sin α−y _t ) ² }
(5)
Therefore, cosξ is expressed by the following equation using the cosine theorem.
cosξ = (BR ² + CR ² −BC ² ) / (2 · BR · CR) (6)
The visible light communication system can receive when the transceiver is within the line-of-sight range, and therefore can communicate when the LED illumination is within the field of view of the receiver. Therefore, communication is possible when the following expression is established.
cosξ> = cosψ _c (7)

The estimated position range (error) increases as the receiver tilt angle increases, and the estimated position has a certain range. This is shown in FIG. FIG. 5A shows a viewing angle of the receiving terminal of 5 deg (degrees), and FIG. 5B shows a case of 20 deg (degrees). In the graph, the horizontal axis shows the x-axis component of the room, and the vertical axis shows the y-axis component.
As shown in FIG. 5A, since the communication area varies depending on the inclination angle θ of the receiver, the position can be identified by combining the inclination data of the receiving terminal and the position information system using visible light. It can be said that. As shown in FIG. 5A, the estimated range increases as the receiver tilt angle θ increases, and the estimated position has a certain range. However, even when the tilt angle θ of the receiver is 60 deg, it is limited to a circle with a diameter of 3 m or less, so if the viewing angle is 5 degrees, it is within the range of 3 m, and in terms of highly accurate position estimation. Achieve the goal.

FIG. 5B shows the case where the FOV of the receiver is changed to 20 deg. FIG. 5B shows the position estimation range depending on the difference in the tilt angle θ of the receiver by comparing with FIG.
The range estimated in the present system increases as the receiver tilt angle θ increases. In the case of FIG. 5B, when the inclination angle θ of the receiving terminal is 60 deg, it is only known that the receiving terminal exists within a wide range as small as 20 m in diameter. Is not very practical or attractive. However, by comparing FIGS. 5A and 5B, it can be seen that the area estimated by narrowing the FOV of the receiving terminal is reduced. Therefore, the position estimation range can be limited by limiting the FOV of the receiver to a narrow angle.

In the position estimation using the position information system of visible light communication, it is considered that the area area estimated by the height of the receiving terminal, that is, the height of the user is affected. Therefore, here, the influence of the height of the receiver is analyzed.
FIG. 6A shows an analysis of the influence on the position estimation range when the height of the receiving terminal is changed between 1.0 m and 2.0 m when the inclination angle θ of the receiver is 60 deg. It is the result of having gone. FIG. 6A shows that the area is shifted in the x-axis direction by changing the height of the receiving terminal. Thus, an error occurs in the position estimated by the height of the terminal when receiving the position information.
Further, it is clear that the influence of the height of the receiving terminal on the position estimation range appears more markedly when the inclination angle θ is larger. However, even when the inclination angle θ is 60 deg, the estimation error due to the height of the receiving terminal is about 4.5 m, so that it can be said that the accuracy is sufficient for guiding a pedestrian in an indoor environment.

If the inclination angle θ of the receiving terminal is 45 degrees or less, the influence on the position estimation range due to the height of the receiving terminal is greatly reduced. Therefore, the height of the receiving terminal does not significantly affect the highly accurate position estimation. it is conceivable that.
FIG. 6B illustrates the case where the inclination angle θ of the receiving terminal is 45 degrees, as in FIG. 6A. At this time, since the error due to the height of the receiving terminal is about 2.5 m, the influence on the position estimation range due to the height of the receiving terminal is reduced by a decrease in the inclination angle θ of the receiving terminal. it is obvious.

In position detection using a 6-axis sensor, the accuracy of the 3-axis acceleration sensor and 3-axis geomagnetic sensor greatly affects the position estimation range. FIG. 7 shows the result of analyzing the position estimation range when the accuracy of the triaxial geomagnetic sensor is ± 6.375 deg and the accuracy of the triaxial acceleration sensor is ± 2 deg.
A range surrounding the elliptical position estimation range in FIG. 7 is a position estimation range in consideration of the accuracy of the six-axis sensor. It can be seen that the estimated area is increased due to the influence of the measurement accuracy of the triaxial acceleration sensor and the triaxial geomagnetic sensor. In addition, the estimated range is relatively large when the tilt angle θ of the receiving terminal is 60 deg. However, since it falls within a circle with a diameter of about 4 m, the GPS positioning accuracy of about 10 m has been greatly improved, and high accuracy is achieved. Position estimation is possible.
When the FOV of the receiving terminal is not limited (FOV 90 deg), the position information transmitted from the light source can be received in a very wide range, as indicated by the area represented by the largest circle in FIG. However, simply limiting the receiver FOV limits the coverage area of the location system, as shown by the small circle in the center in FIG. Very difficult to use because it cannot be detected.

In the present invention, the FOV of the receiving terminal is limited, and the absolute position information is obtained by the visible light position transmission system while using the tilt data of the 6-axis sensor, so that the estimated area is reduced and other than directly under the LED illumination. But positioning is possible. When the tilt data of the 6-axis sensor is not used, the area of the large circle that is the receivable area of the visible light position transmission system in the case of FOV 90 deg is approximately 177 m ² , whereas the FOV is limited to 5 deg and tilt data When the inclination angle θ of the receiving terminal is 60 deg and the accuracy of the 6-axis sensor is considered, the range (the largest elliptical area in FIG. 7 + the area surrounding the largest ellipse) is About 9 m ² .
As a result, in the present invention, it is possible to limit the estimated area to about 5% as compared with the case where the visible light position information is simply received. Therefore, by using the method of the present invention, the positioning accuracy can be improved 20 times in terms of area ratio.
As described above, it is difficult to estimate the position with high accuracy by accumulating errors using only sensor positioning, but in addition to the information from the visible light transmitter that transmits the absolute position, the tilt data of the 6-axis sensor is used. Thus, the present system for estimating the current position of the user having the terminal solves the problem of error accumulation and enables highly accurate position estimation.

As described above, in this system, the problem can be solved from the viewpoint of infrastructure maintenance by assuming an LED illuminator as a visible light transmitter and a light receiving element mounted on, for example, a mobile phone as a receiving terminal.
In addition, the position can be estimated by using an existing system without using a complicated device such as an image sensor.
Furthermore, by combining a visible light transmitter and a 6-axis sensor, it is possible to simultaneously solve the problem of error accumulation of sensor positioning and infrastructure maintenance of local positioning. In addition to realizing estimation, there is a possibility that seamless location services indoors and outdoors can be constructed.
Therefore, it can be said that this system can be expected as a method for estimating the position with high accuracy.

It is a figure for demonstrating the outline | summary of this system. It is a figure for demonstrating the principle of this system. It is a figure explaining the structure of the terminal in this system. It is a figure explaining calculation of a position in this system. It is a figure explaining the influence of the viewing angle (FOV) of the terminal in this system. It is a figure explaining the influence of the height of the terminal in this system. It is a figure explaining the influence of the error of the sensor in this system.

Claims (4)

A light source that transmits the information of the installed position by visible light; and
A visible light receiving terminal including a 3-axis acceleration sensor, a 3-axis geomagnetic sensor, a visible light receiving unit that receives position information from a light source, and a calculation unit;
The receiving terminal is corrected by the calculation unit based on the position information of the light source received by the visible light receiving unit, the three-dimensional posture information by the three-axis acceleration sensor, and the three-dimensional direction by the three-axis geomagnetic sensor. A position information acquisition system characterized in that the position information of a terminal is calculated.   The position information acquisition system according to claim 1, wherein the visible light receiving unit of the receiving terminal has a predetermined viewing angle. A visible light receiving terminal comprising: a three-axis acceleration sensor; a three-axis geomagnetic sensor; a visible light receiving unit that receives position information from a light source;
Position information of the terminal corrected by the calculation unit based on the position information of the light source received by the visible light receiving unit, the three-dimensional orientation information by the three-axis acceleration sensor, and the three-dimensional direction by the three-axis geomagnetic sensor A visible light receiving terminal characterized by calculating   The visible light receiving terminal according to claim 3, wherein the visible light receiving unit has a predetermined viewing angle.